In order to prevent the lowering of electrical performance of electrical contacts due to oxidation or sulfuration of silver or alloys thereof which form the contact surfaces of the electrical contacts, it has been suggested to have said contact surfaces plated or clad in a thickness of 1-15.mu. by gold, palladium, or alloys thereof which scarcely react with an environmental gas atmosphere. Such employment is effective for a certain extent when the electric density exerted on contact surfaces is comparatively low. However, when contacts are charged with electric current of a high density and they are exposed to arcs of a high temperature resulting from the opening and closing cycle of the contacts, gold, palladium, or alloys thereof which lie over the contact surfaces are scattered off from said surfaces or melt deeply all together into matrices of contacts, whereby the metals can not perform as well as desired.
Lately, it has been proposed and applied to have silver or silver alloy matrices dispersed with metal oxides such as Sn, Sb, Zn, In, and Bi oxides, so that contacts made therefrom can exhibit, on account of high refractoriness of the metal oxides, high anti-weldability and low-electric contact resistance, even when electric current of a high density is applied thereto. To our disappointment, however, employment of a precious metal of the kind mentioned above for plating or cladding surfaces of the just above-mentioned contacts exhibits little effect or brings forth adverse effects. To wit, since said silver-base contacts which are dispersed with refractory metal oxides are thermally highly stable, and hardly agitate even when their surfaces are subjected to arcs of a high temperature, which are frequently produced particularly at their initial stages of use, and since the more the contact surfaces are thus thermally stable, the more difficult it is to apply gold, palladium, or their alloys to such contact surfaces, because said precious metals are agitated one-sidedly when they are subjected to arcing heat, and they tend to be isolated from and coagulate spherically on the contact surfaces, resulting in the occurrence of undesirable welding of contacts and subsequent inability of making and breaking thereof.